U.S. Pat. No. 3,451,871 to Bauer discloses a process wherein a metal sheet is treated with an electric field to improve the adherance of a second material, such as adhesive or plastic film. The second material may also be a metal.
Cohen et al U.S. Pat. No. 3,699,334 is directed to a process wherein the metal surface is eroded by ion bombardment. These ions are preferably argon, and the process is used in surface shaping.